1. Field of the Invention
The present invention relates to a CFI-type zeolite containing fourteen-membered ring pores useful as a conversion catalyst for organic compounds, a process for the preparation of the zeolite, a catalyst prepared from the zeolite, and a process for the conversion of organic compounds.
2. Description of Related Arts
The CFI-type zeolite is a zeolite containing novel fourteen-membered ring pores invented by Yoshikawa and Devis and also is called CIT-5. Processes for the synthesis and the structure of the zeolite are already disclosed by the following literatures:
Literature 1: WO99/08961
Literature 2: Chemical Communications, 2179 (1997)
Literature 3: Journal of Physical Chemistry, B, 102, 7139 (1998)
Literature 4: Journal of Catalysis, 182, 463 (1999)
Literature 5: Shokubai, 41, 380 (1999)
Literature 2 describes CIT-5 having a SiO2/Al2O3 ratio of 50, but no physical shape thereof. Furthermore, the CIT-5 having a SiO2/Al2O3 ratio of 50 could not be prepared according to the process as described therein. As described in Example 5 of literature 1, hydrothermal treatment of the reaction mixture having a known composition (LiOH/SiO2=0.1and methylsparteinium hydroxide/SiO2=0.2) only produces a mixture containing amorphous materials without forming a finely crystallized CFI-type zeolite from the reaction mixture having a SiO2/Al2O3 ratio of 100. The other literatures describe no CIT-5 having a SiO2/Al2O3 ratio lower than 100, and also no CIT-5 having an atomic ratio of silicon to a heteroatom that is 45 or less. In literature 1, the synthesis of CIT-5 is carried out by use of the reaction mixture having a Si/Zn ratio of 25, but it is not clear whether zinc is contained in the resulting zeolite.
The CFI-type zeolite (CIT-5) contains a fourteen-membered ring pore which is large of the pore sizes of zeolites, and is expected as a novel material for catalysts. However, the related art has been unable to introduce a number of heteroatoms into the framework of the zeolite, that is, producing only CIT-5 having a small number of catalytic active sites. CIT-5 has a monodimensional pore of fourteen-membered ring size. The monodimensional pore is inferior in diffusion to multi-dimensional pores, and therefore smaller crystals are useful as catalysts. However, the related art has been unable to prepare CIT-5 having a number of active sites and furthermore small crystal size.
The invention aims at providing CIT-5 having a number of active sites and small crystal size, and more concretely a CFI-type zeolite where the atomic ratio of silicon to the heteroatom is 45 or less, and the long axes of the crystals are 0.7 xcexcm or less.
The first invention of the invention is the CFI-type zeolite characterized in that the atomic ratio of silicon to the heteroatom is 45 or less, and the long axes of the crystals are 0.7 xcexcm or less.
The second invention is a process for preparing the CFI-type zeolite characterized in that a reaction mixture satisfying the following both conditions (1) and (2) is subjected to hydrothermal treatment:
(1) LiOH/SiO2 less than 0.15 (in molar ratio)
(2) ROH/SiO2 greater than 0.2 (in molar ratio, ROH represents an alkylsparteinium hydroxide).
The third invention is a catalyst containing the aforesaid CFI-type zeolite.
The fourth invention is a process for the conversion of organic compounds characterized by allowing the aforesaid catalyst to contact with the organic compounds.